The invention relates to hand-held wireless communication devices (HHWCDs), such as hand-held data devices, cellular telephones, and the like, having an antenna. In particular, the invention relates to such devices having an antenna system, the antenna system including a parasitic element. The antenna system can be internal or partially internal to the device. The HHWCDs having antennas according to the present invention may be used for transmitting, receiving or for transmitting and receiving.
Dipoles, both symmetric and asymmetric, monopoles, and slot antennas provide linear polarization and a doughnut antenna pattern in free space.
Crossed dipoles or slots, referred to as a turnstile antenna, produce circular polarization and near-hemispherical antenna pattern.
Helices provide circular polarization and directivity. Quadrifilar helices provide circular polarization, and near-hemispherical antenna pattern.
Patch antennas provide hemispherical antenna pattern and circular polarization.
Arrays of monopole, dipole, or loop elements provide directivity and linear polarization.
A principal object of the invention is to control the antenna radiation pattern of a HHWCD antenna.
A related object of the invention is to control the antenna radiation pattern of a HHWCD antenna without increasing the size of the HHWCD.
Another object, applicable only to some of the described embodiments, is to provide a simple low-cost internal antenna system for HHWCDs, suitable for high volume manufacturing and eliminating the susceptibility to damage of external antennas.
Another objective of the invention is to use the existing printed wiring board (PWB) or printed circuit board (PCB) of a HHWCD as part of an internal or partly internal antenna system.
According to the teachings of the present invention, HHWCDs have an antenna system comprising an asymmetrical dipole driven element with a planar resonator element or section and a planar radiating element or section, in conjunction with a thin planar parasitic element closely spaced to the driven element, particularly the planar radiating section thereof The radiating planar section may be the ground traces of the HHWCD""s printed wiring board (PWB). The resonator element may be planar and configured as a meandering or serpentine conductor in order to save space and allow the antenna to be totally internal within the device. Such a resonator has negligible radiation because of its configuration. Alternatively, the resonator need not be planar and need not be internal. The resonator may be, for example, an essentially quarter-wavelength straight or coiled wire, mounted externally or an essentially quarter-wavelength planar inverted-F. In the case of an internal planar meandering or serpentine conductor, the resonator""s conductor may be the conductive printed wiring trace on a PWB dielectric, a metal stamping, or the like.
In accordance with the present invention, a hand held wireless communications device comprises an enclosure for the device and an antenna, at least partly within the enclosure. The antenna operates within a frequency band and includes a driven element and a thin planar parasitic element. The parasitic element has a generally square configuration wherein the major dimensions of the parasitic element are about a half wavelength within the frequency band. The parasitic element is spaced from the driven element by 0.01 to 0.1 wavelength within the frequency band.
The antenna has dual polarization in some directions and three polarizations in some directions.
The peak gain of a classic dipole antenna or array of dipoles is in a direction perpendicular to the long axis of the dipole. The peak gain of the antenna of the HHWCD of the present invention is nearly normal to the fed dipole axis in one plane and is in one direction, at approximately 195 degrees, as shown in FIG. 5 (described further below). In another plane, the peak gain occurs at angles of approximately 45 and 70 degrees away from the direction perpendicular to the dipole""s major axis as shown in FIGS. 2 and 3 (described further below). As will be understood more fully in connection with the antenna patterns described below, this antenna exhibits maximum forward gain on the order of +3 dBi and maximum front-to-back ratio on the order of 7 dB. The antenna demonstrates the characteristic of having two orthogonal polarizations that may combine to result in circular polarization.
The pattern of the antenna is thought to be a result of the placement, size, and design of the asymmetric dipole and the parasitic plate conductor. The front-to-back directivity can be utilized to reduce energy in the direction of a user of the HHWCD, while increasing energy in the opposite direction. The polarization diversity minimizes fading caused by multipath, a common problem with HHWCDs.